1. Field of the Invention
The invention relates to a method of manufacturing a thin film magnetic head having at least an inductive magnetic transducer for writing.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in a surface recording density of a hard disk drive. A composite thin film magnetic head, which has a stacked structure comprising a recording head having an inductive magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinafter referred to as MR) element for reading, is widely used as the thin film magnetic head.
The increase of the recording density of the performance of the recording head requires the increase of a track density on a magnetic recording medium. For this purpose, it is necessary to realize a recording head having a narrow track structure in which the on-air-bearing-surface widths of a top pole and a bottom pole, which are formed on and under a write gap, respectively, with the write gap in between, are as narrow as a few microns to the submicron order. Semiconductor processing technology is used in order to achieve this recording head.
A method of manufacturing a composite thin film magnetic head will be now described with reference to FIGS. 36 to 41, as an example of a conventional method of manufacturing a thin film magnetic head.
In the method of manufacturing, first, as shown in FIG. 36, an insulating layer 102 made of, for example, aluminum oxide (Al2O3, hereinafter referred to as xe2x80x9caluminaxe2x80x9d) is deposited with a thickness of about 5.0 xcexcm to about 10.0 xcexcm on a substrate 101 made of, for example, altic (Al2O3xe2x80x94TiC). Then, a bottom shield layer 103 for a reproducing head is formed on the insulating layer 102. Then, for example, an alumina layer is deposited by sputtering with a thickness of 100 nm to 200 nm on the bottom shield layer 103, and thus a shield gap film 104 is formed. Then, an MR film 105 for forming an MR element for reproducing is formed with a thickness of a few tens of nanometers on the shield gap film 104, and the MR film 105 is patterned into a desired shape by high-accuracy photolithography. Then, lead layers (not shown) for functioning as lead electrode layers to be electrically connected to the MR film 105 are formed on both sides of the MR film 105. After that, a shield gap film 106 is formed on the lead layers, the shield gap film 104 and the MR film 105, and thus the MR film 105 is sandwiched in between the shield gap films 104 and 106. Then, a top shield-cum-bottom pole (hereinafter referred to as a bottom pole) 107 made of a magnetic material for use in both the reproducing and recording heads, e.g., a nickel-iron alloy (NiFe, hereinafter referred to as xe2x80x9cPermalloy (a trade name)xe2x80x9d) is formed on the shield gap film 106.
Then, as shown in FIG. 37, a write gap layer 108 made of an insulating material, e.g., alumina is formed on the bottom pole 107, and a photoresist film 109 is formed into a predetermined pattern on the write gap layer 108 by high-accuracy photolithography. Then, a thin film coil 110 made of, for example, copper (Cu) for an inductive recording head is formed on the photoresist film 109 by plating, for example. Then, a photoresist film 111 is formed into a predetermined pattern by high-accuracy photolithography so as to coat the photoresist film 109 and the thin film coil 110. Then, the photoresist film 111 is subjected to heat treatment at a temperature of, for example, 250xc2x0 C. in order to provide insulation among windings of the thin film coil 110.
Then, as shown in FIG. 38, the write gap layer 108 is partially etched at a more rearward position than the thin film coil 110 (on the right side in FIG. 38) in order to form a magnetic path, whereby an opening 108a is formed and thus a part of the bottom pole 107 is exposed. Then, a magnetic material having high saturation magnetic flux density, e.g., Permalloy is formed into a film by electroplating so as to coat an exposed surface of the bottom pole 107, the photoresist film 111 and the write gap layer 108. Then, the plated film made of Permalloy is selectively etched by ion milling using a mask (not shown) made of a photoresist film having a predetermined planar shape, and thus a top yoke-cum-top pole (hereinafter referred to as a top pole) 112 is formed. For example, the top pole 112 has a planar shape shown in FIG. 41 to be described later and includes a yoke portion 112a and a pole chip portion 112b. The top pole 112 is in contact with and magnetically coupled to the bottom pole 107 in the opening 108a. Then, both the write gap layer 108 and the bottom pole 107 are selectively etched by about 0.5 xcexcm by ion milling using a part (the pole chip portion 112b) of the top pole 112 as a mask (see FIG. 40), and thereafter an overcoat layer 113 made of, for example, alumina is formed on the top pole 112. Finally, a track surface of the recording head and the reproducing head, i.e., an air bearing surface 120 is formed by machining and polishing, and, as a result, a thin film magnetic head is completed.
FIGS. 39 to 41 show the structure of the completed thin film magnetic head. FIG. 39 shows a cross section of the thin film magnetic head in a direction perpendicular to the air bearing surface 120. FIG. 40 shows an enlarged view of a cross section of a pole portion in a direction parallel to the air bearing surface 120. FIG. 41 shows a planar structure of the thin film magnetic head. FIG. 38 corresponds to a cross section viewed from the direction of the arrows along the line XXXVIIIxe2x80x94XXXVIII of FIG. 41. The overcoat layer 113 and so on are not shown in FIGS. 39 to 41. In FIG. 41, the thin film coil 110 and the photoresist film 111 are shown, but their outermost ends alone are shown.
In FIGS. 39 and 41, xe2x80x9cTHxe2x80x9d indicates a throat height, and xe2x80x9cMRHxe2x80x9d indicates an MR height. The xe2x80x9cthroat height (TH)xe2x80x9d refers to one of factors that determine the performance of the recording head, and refers to a length between the position of an edge of the insulating layer (the photoresist film 111) for electrically isolating the thin film coil 110 from the other conductive portions, which is closest to the air bearing surface 120, i.e., a throat height zero position (a THO position) and the position of the air bearing surface 120. The optimization of the throat height (TH) is desired for the improvement in the performance of the recording head. The throat height (TH) is controlled by the amount of polishing of the air bearing surface 120. The xe2x80x9cMR height (MRH)xe2x80x9d refers to a length between the position of a farthest edge of the MR film 105 from the air bearing surface 120, i.e., an MR height zero position (an MRH0 position) and the position of the air bearing surface 120. The MR height (MRH) is also controlled by the amount of polishing of the air bearing surface 120.
Factors that determine the performance of the thin film magnetic head include an apex angle (xcex8) shown in FIG. 39, in addition to the throat height (TH), the MR height (MRH) and so on. The apex angle xcex8 refers to an average degree of inclination of an inclined surface of the photoresist film 111 close to the air bearing surface 120.
As shown in FIG. 40, a structure in which the respective parts of both the write gap layer 108 and the bottom pole 107 are etched in self-alignment with the pole chip portion 112b of the top pole 112 is called a trim structure. The trim structure can prevent the increase in an effective track width resulting from a spread of a magnetic flux generated during writing data on a narrow track. In FIG. 40, xe2x80x9cP2Wxe2x80x9d indicates a width of a portion (hereinafter referred to as xe2x80x9ca pole portion 500xe2x80x9d) having the trim structure, namely, a pole width (hereinafter sometimes referred to as xe2x80x9ca track widthxe2x80x9d). In FIG. 40, xe2x80x9cP2Lxe2x80x9d indicates a thickness of the pole chip portion 112b forming a part of the pole portion 500, namely, a pole length. As shown in FIG. 40, lead layers 121 for functioning as lead electrode layers to be electrically connected to the MR film 105 are provided on both sides of the MR film 105. The lead layers 121 are not shown in FIGS. 36 to 39.
As shown in FIG. 41, the top pole 112 has the yoke portion 112a occupying most of the top pole 112, and the pole chip portion 112b having a substantially uniform width as the pole width P2W. An outer edge of the yoke portion 112a forms an angle xcex1 with a surface parallel to the air bearing surface 120 at a coupling portion between the yoke portion 112a and the pole chip portion 112b, and an outer edge of the pole chip portion 112b forms an angle xcex2 with the surface parallel to the air bearing surface 120 at the above-mentioned coupling portion. For example, xcex1 is about 45 degrees, and xcex2 is 90 degrees. As described above, the pole chip portion 112b is a portion to be used as a mask for forming the trim structure of the pole portion 500. As can be seen from FIGS. 39 and 41, the pole chip portion 112b extends on the flat write gap layer 108, and the yoke portion 112a extends on a coil portion (hereinafter referred to as xe2x80x9can apex portionxe2x80x9d), which is coated with the photoresist film 111 and rises like a hill.
Detailed structural features of the top pole are described in Unexamined Japanese Patent Application Publication No. Hei 8-249614, for example.
Since the pole width P2W of the pole portion 500 defines a write track width on the recording medium, the increase of the recording density requires narrowing of the pole width P2W by forming the pole portion 500 with high accuracy. Too great a pole width P2W causes the occurrence of a phenomenon in which data is written on adjacent regions as well as a predetermined write track region on the recording medium, i.e., a side erase phenomenon, and consequently the recording density cannot be improved. Therefore, it is important to narrow the pole width P2W of the pole portion 500 and to make the pole width P2W uniform over a direction of thickness (a vertical direction in FIG. 40) and a direction of length (a horizontal direction in FIG. 39).
Methods of forming the top pole 112 include, in addition to a wet process such as frame plating, a dry process of patterning a plated film made of Permalloy by selectively etching the plated film by means of ion milling as described above, for example.
However, the applicant and so on have found out that this method using ion milling causes the following problems. For example, when a surface of a plated film is irradiated with ion beams from a direction substantially perpendicular to the surface of the plated film (a direction that forms an angle of about 0 to 30 degrees with the normal to the surface of the plated film), an etching product generated during etching is redeposited on a non-etched portion, and thus the width of the pole chip portion 112b is partly greater than a designed value. For example, when a surface of a plated film is irradiated with ion beams from a direction substantially parallel to the surface of the plated film (a direction that forms an angle of about 50 to 70 degrees with the normal to the surface of the plated film), the above-mentioned phenomenon of redeposition of the etching product is avoided, but the amount of etching increases as the process proceeds, and thus the width of the pole chip portion 112b is partly smaller than the designed value. In particular, when the pole portion 500 is formed by using ion milling under the latter conditions, the pole width P2W becomes nonuniform as shown in FIG. 42.
In a conventional method, a photoresist film for forming a mask (a photoresist pattern) to be used for patterning a plated film is formed on an underlayer (a Permalloy layer) having a concave and convex structure. Thus, during exposure, light is reflected obliquely or transversely from a surface of the underlayer, the reflected light increases or reduces an exposed region, and, as a consequence, the accuracy in forming the mask deteriorates. The deterioration in the accuracy in forming the mask is also caused by that Permalloy having relatively high reflectance is used as a material of the plated film that is the underlayer of the photoresist film.
In the conventional method, the pole portion 500 is formed by ion milling having a low etching rate, thus an etching process takes a long time, and therefore a considerable time is required for the completion of processing of the pole portion 500. This tendency manifests itself not only during forming the pole portion 500 but also during forming the top pole 112 and other magnetic layer portions (the bottom shield layer 103, the bottom pole 107, etc.).
The invention is designed to overcome the foregoing problems. It is an object of the invention to provide a method of manufacturing a thin film magnetic head, which enables forming a thin film magnetic head with high accuracy in a short time.
There is provided a method of manufacturing a thin film magnetic head of the invention having: a first magnetic layer and a second magnetic layer magnetically coupled to each other having two magnetic poles which face each other with a gap layer in between and are to be faced with a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers, the first magnetic layer having a first magnetic layer portion that includes a first uniform-width portion extending away from a recording-medium-facing surface to be faced with the recording medium and defining a write track width on the recording medium, and a second magnetic layer portion that extends in a region in which the thin film coil portion is provided and that is magnetically coupled to the first magnetic layer portion, the second magnetic layer having a second uniform-width portion corresponding to the first uniform-width portion of the first magnetic layer, wherein at least one of the step of forming the first magnetic layer and the step of forming the second magnetic layer includes the steps of: forming a magnetic material layer; polishing and flattening a surface of the magnetic material layer; forming a first mask on the magnetic material layer flattened; and selectively etching the magnetic material layer by reactive ion etching using the first mask.
In the method of manufacturing a thin film magnetic head of the invention, the first mask is formed on a flat surface of the magnetic material layer, and the magnetic material layer is selectively etched by reactive ion etching using the first mask, whereby at least one of the first magnetic layer and the second magnetic layer is formed.
In the method of manufacturing a thin film magnetic head of the invention, an inorganic material may be used as a material of the first mask. Preferably, a material containing aluminum oxide or aluminum nitride is used as the inorganic material.
In the method of manufacturing a thin film magnetic head of the invention, a planar shape of the first mask may include a portion corresponding to a planar shape of at least the first uniform-width portion of the first magnetic layer portion.
When the first magnetic layer portion further includes a wide portion being located in an opposite side of the first uniform-width portion from the recording-medium-facing surface, being magnetically coupled to the first uniform-width portion and having a greater width than a width of the first uniform-width portion, when a step is formed in a width direction at a coupling position between the first uniform-width portion and the wide portion, and when a corner is formed with a side edge surface of the first uniform-width portion and a step surface of the wide portion at the step, it is preferable that the first mask is formed so as to include a portion having a planar shape corresponding to a planar shape of the wide portion and that an angle of a portion of the first mask, the portion corresponding to the corner of the first magnetic layer portion, be within a range of 90 degrees to 120 degrees.
In the method of manufacturing a thin film magnetic head of the invention, the step of forming the first mask may include the steps of: forming a mask precursory layer made of an inorganic material on the surface of the magnetic material layer; forming a second mask on a surface of the mask precursory layer; and forming the first mask by patterning the mask precursory layer by use of the second mask. Preferably, the mask precursory layer is patterned by reactive ion etching at a temperature within a range of 50xc2x0 C. to 300xc2x0 C. in a gaseous atmosphere containing at least one of chlorine and boron trichloride.
In the method of manufacturing a thin film magnetic head of the invention, a metal film pattern having a predetermined shape which is formed on the surface of the mask precursory layer may be used as the second mask, or a photoresist film pattern having a predetermined shape which is formed on the surface of the mask precursory layer may be used as the second mask. When the metal film pattern is used as the second mask, the metal film pattern may be formed by selectively growing a plated film on the surface of the mask precursory layer, or the metal film pattern may be formed by selectively etching a metal layer formed on the surface of the mask precursory layer.
In the method of manufacturing a thin film magnetic head of the invention, at least the first uniform-width portion of the first magnetic layer may be formed by the step of processing, or at least the second uniform-width portion of the second magnetic layer may be formed by the step of selectively etching the magnetic material layer.
In the method of manufacturing a thin film magnetic head of the invention, a region of the gap layer excluding a portion corresponding to the first uniform-width portion of the first magnetic layer may be selectively removed by reactive ion etching. Preferably, formation of the first uniform-width portion of the first magnetic layer, selective removal of the gap layer, and formation of the second uniform-width portion of the second magnetic layer are successively performed. To process the above-mentioned portions, it is preferable that the first mask made of an inorganic material be used to form the first uniform-width portion of the first magnetic layer and that at least one of the first mask and the first uniform-width portion be used as an etching mask to selectively remove the gap layer and form the second uniform-width portion of the second magnetic layer.
In the method of manufacturing a thin film magnetic head of the invention, in the step of forming the first magnetic layer, the second magnetic layer portion may be selectively formed from the first magnetic layer portion by patterning using reactive ion etching. Preferably, the second magnetic layer portion is formed in such a manner that the second magnetic layer portion partly overlaps the first magnetic layer portion and that the edge thereof close to the recording-medium-facing surface is located far from the position of the recording-medium-facing surface.
In the method of manufacturing a thin film magnetic head of the invention, when the thin film coil portion has a first thin film coil and the insulating layer has a first insulating layer portion which the first thin film coil is embedded in, the method may include the steps of: forming the first insulating layer portion so as to cover at least the first magnetic layer portion and the first thin film coil; and forming a first flat surface by polishing a surface of the first insulating layer portion until at least the first magnetic layer portion is exposed. In this case, the second magnetic layer portion may be formed on the first flat surface in such a manner that the second magnetic layer is brought into contact with the first magnetic portion exposed.
In the method of manufacturing a thin film magnetic head of the invention, when the first magnetic layer further includes a third magnetic layer portion for magnetically coupling the first magnetic layer portion to the second magnetic layer portion between the first magnetic layer portion and the second magnetic layer portion, the third magnetic layer portion may be formed on the first flat surface by reactive ion etching. Preferably, the third magnetic layer portion is formed in such a manner that the third magnetic layer portion partly overlaps both of the first magnetic layer portion and a part of the second magnetic layer portion and that the edge thereof close to the recording-medium-facing surface is located far from the position of the recording-medium-facing surface.
In the method of manufacturing a thin film magnetic head of the invention, when the thin film coil portion further has a second thin film coil provided in a different layer from the first thin film coil and the insulating layer further has a second insulating layer portion which the second thin film coil is embedded in, the method may include the steps of: forming a first connecting pattern on an end of the second thin film coil simultaneously with forming the second thin film coil, the first connecting pattern being a part of the thin film coil portion and being integral with the second thin film coil; forming a second connecting pattern on the first connecting pattern simultaneously with forming the third magnetic layer portion, the second connecting pattern being a part of the thin film coil portion; forming the second insulating layer portion so as to coat at least the third magnetic layer portion, the second thin film coil and the second connecting pattern; forming a second flat surface by polishing a surface of the second insulating layer portion until at least both of the third magnetic layer portion and the second connecting pattern are exposed; and forming a conductive layer pattern on the second flat surface so as to be electrically connected to an exposed surface of the second connecting pattern. In this case, the second magnetic layer portion may be further formed on the second flat surface.
In the method of manufacturing a thin film magnetic head of the invention, when the thin film magnetic head further has a magnetic transducer film extending away from the recording-medium-facing surface and a third magnetic layer for magnetically shielding the magnetic transducer film, the third magnetic layer may be formed by patterning with reactive ion etching.
In the method of manufacturing a thin film magnetic head of the invention, the magnetic material layer is formed by sputtering using a predetermined magnetic material. Preferably, a material containing iron nitride, or an amorphous alloy such as a material containing a zirconium-cobalt-iron alloy is used as the magnetic material.
In the method of manufacturing a thin film magnetic head of the invention, it is preferable that the step of selectively etching the magnetic material layer be performed at a temperature within a range of 50xc2x0 C. to 300xc2x0 C. in a gaseous atmosphere containing at least one of chlorine, boron trichloride and hydrogen chloride.
Other and further objects, features and advantages of the invention will appear more fully from the following description.